In general, computer models used to predict weather use around seven equations that govern how the basic parameters—temperature, pressure, and so on—change over time in the atmosphere. Scientists call the study of how they can physically and mathematically represent all the processes in the atmosphere dynamics.

In reality, everyone knows computer models can’t perfectly predict the weather at this time. This is because of several factors, including errors in the initial conditions (or the observations the model gets to begin making its forecast) and errors inherent in the model (a computer model can’t take into consideration all the factors controlling the weather). Long-term forecasts are even more inaccurate because these two errors are compounded mathematically over time.